Field Of Energy Conversion Research Articles

Design strategy for high-performance bifunctional electrode materials with heterogeneous structures formed by hydrothermal sulfur etching

The synthesis of efficient, stable, and green multifunctional electrode materials is a long-standing challenge for modern society in the field of energy storage and conversion. To this end, we successfully synthesized five bimetallic precursor materials with excellent performance by hydrothermal reaction with the assistance of a high concentration of polyvinylpyrrolidone (PVP), and then, sulfide etched the lamellar precursor materials among them to obtain the one-dimensional heterostructured samples. Benefiting from the synergistic effect of the bimetal and the continuous electron/ion transport structure, the samples displayed excellent bifunctional activity in supercapacitor and oxygen evolution reaction (OER). Regarding supercapacitors, the exceptional performance of 2817.2 F g−1 at 1 A g−1 was demonstrated, while the asymmetric supercapacitors made showed an extraordinary energy density of 150.2 Wh kg−1 at a power density of 618.5 W kg−1 and outstanding cycling performance (94.74% capacity retention after 20,000 cycles at 10 A g−1). Simultaneously, a wearable flexible electrode that can be wrapped around a finger was coated on a carbon cloth and was found to light up a 0.5-m-long strip of light. Moreover, it exhibited an ultralow oxygen reduction overpotential of 249 mV at 10 mA cm−2. Hence, our work provides a facile strategy to modulate the synthesis of heterogeneous structured sulfides with a continuous electron/ion transport pathway, which possesses excellent oxygen reduction electrocatalytic performance while meeting superior supercapacitor performance. Such work provides an effective approach for the construction of multifunctional electrochemical energy materials.

Momordica Grosvenori Shell-Derived Porous Carbon Materials for High-Efficiency Symmetric Supercapacitors.

Porous carbon materials derived from waste biomass have received broad interest in supercapacitor research due to their high specific surface area, good electrical conductivity, and excellent electrochemical performance. In this work, Momordica grosvenori shell-derived porous carbons (MGCs) were synthesized by high-temperature carbonization and subsequent activation by potassium hydroxide (KOH). As a supercapacitor electrode, the optimized MGCs-2 sample exhibits superior electrochemical performance. For example, a high specific capacitance of 367 F∙g-1 is achieved at 0.5 A∙g-1. Even at 20 A∙g-1, more than 260 F∙g-1 can be retained. Moreover, it also reveals favorable cycling stability (more than 96% of capacitance retention after 10,000 cycles at 5 A∙g-1). These results demonstrate that porous carbon materials derived from Momordica grosvenori shells are one of the most promising electrode candidate materials for practical use in the fields of electrochemical energy storage and conversion.

Polymer‐derived ceramics for electrocatalytic energy conversion reactions

AbstractPolymer‐derived ceramics (PDCs) are being actively explored in various fields today because of their unique physiochemical properties. Very recent advances in the use of PDCs in energy storage technologies (e.g., batteries, supercapacitors) have motivated researchers to explore the possibilities of PDCs as electrocatalysts for use in energy conversion reactions. Impressively, the tunable functional properties, especially the electrical properties, of PDCs have helped to break through this “bottleneck” and enabled them to become promising materials for use in electrocatalytic conversion. This review presents an in‐time summary of the progress in the development of PDCs for electrochemical energy conversion. First, a general introduction to the preparation of PDCs is provided. Later, the factors (e.g., chemical stability, electron conductivity) most closely related to electrocatalytic performance are discussed. Specifically, the parameters that affect the electron conductivity of PDCs are enumerated to delve into advanced strategies for achieving effective electrocatalysts. The relevant electrocatalytic conversion reactions (e.g., hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction) and utilization of PDCs in these reactions are also comprehensively introduced. Finally, the current challenges and future opportunities for PDC materials in the field of electrochemical energy conversion are summarized.

Synergy between copper single atoms and cobalt particles for high performance frigostable aqueous Al-air batteries

The performance of Al-air batteries remain stagnant due to sluggish air cathode reactions, especially in cold environments. Therefore, it is urgent to explore aqueous Al-air batteries to equip an efficient catalyst for application under low temperature. Here, copper single atoms (Cu1) and cobalt particles (Cop) decorated N doped carbon (Cu1CopNC) were synthesized via carbonization of Cu, Co co-doped ZIF-8 combined with MWCNTs. The synergistic effect in Cu1-Cop active sites and unique 1D-3D porous nanostructure endow Cu1CopNC with high oxygen reduction activities: high onset and half-wave potential (0.98 V and 0.87 V vs RHE, respectively). Consequently, the Al-air batteries with Cu1CopNC show remarkable performance in a wide service temperature range (-40–50 ℃). Such alkaline Al-air battery provides a high start voltage from 0.7 V with a peak power density of about 16.58 mW cm−2 at −40 ℃. It is expected that such metal single atoms with neighbored heterogeneous metallic particles could be extended in various energy conversion and storage fields.

Oxygen reduction activity of a Pt-N4 single-atom catalyst prepared by electrochemical deposition and its bioelectrochemical application

The oxygen reduction reaction (ORR) is important in the field of energy conversion. Single-atom (SA) catalysts (SACs) exhibit good ORR catalytic effects and are widely used in electrocatalysis. Herein, we broaden the application of SACs in the field of bioelectrochemistry and study their electrocatalytic performance in air-cathode microbial fuel cells (MFCs). In this study, a platinum (Pt) SA-skin catalyst, boron-nitride-carbon (BCN) nanosheet with densely accessible Pt-N4 moieties named Pt SAs-BCN, was prepared by electrochemical deposition, which is more beneficial for large-scale industrial preparation of SACs. The obtained Pt SAs-BCN offered numerous active sites with adequate exposure, resulting in highly efficient and stable ORR activity. The participation of trace Pt SAs strengthens the electrocatalytic performance of BCN and reduces its charge transfer resistance. Remarkably, when employed as an air cathode in MFCs, the Pt SAs-BCN-modified MFC exhibited a maximum power generation capacity of 0.425 V and a maximum power density of 936.31 mW cm−2, while being able to run for two months without a violent performance drop. The application of SACs in the field of bioelectrochemistry achieves the purpose of energy conversion and has great potential for the bioelectrodegradation of organics.

Recent advances in interfacial engineering and band-gap tuning of perovskite multiferroic heterostructures for high performance photovoltaic applications

The increasing environmental pollution generated by the conventional sources of energy and the crises created via extensive use of fossil fuels, especially global warming, forces humanity to develop innovative technologies to utilize renewable and sustainable energy sources such as solar radiation. The present efficiency of conventional silicon-based bipolar heterojunctions used in solar panels, could be improved employing the potential of the photovoltaic properties of multiferroic materials in novel polarization driven carrier-based devices. In a span of a few years, the multiferroic films are in the center of attraction of researchers in the field of solar energy conversion due to their excellent efficiency of ferroelectric polarization-driven carrier separation, possible magnetism-photon coupling, and the high yield of the photo-voltage above the band-gap. In this featured letter, the focus is on critically reviewing the advances on multiferroic structure, new possibilities in this direction and future scopes and challenges for their role in increasing the photovoltaic response via interfacial engineering and band-gap tuning..

Realizing efficient exciton dissociation in an all-organic heterojunction photocatalyst for highly improved photocatalytic H2 evolution

Although graphitic carbon nitride is a promising photocatalyst in the field of energy conversion and environmental purification, the intrinsic properties like excitonic effects and sluggish charge transfer restrict further photocatalytic applications. To circumvent these limitations, the novel all-organic heterojunction photocatalysts were constructed by anchoring organic carbon dots (O-dots) on porous graphitic carbon nitride nanosheets (O-dots/CNS). Results demonstrated that excitons can be effectively dissociated into electrons and holes at the interface of O-dots/CNS heterojunction, followed by holes injected to O-dots and electrons accumulated in CNS to realize efficient charge separation. Consequently, the O-dots/CNS with the optimized hydrogen (H2) evolution performance could be reached 1564.5 μmol h−1g−1 under the visible light irradiation. This work not only presents new ideas for rational design photocatalytic reaction system from exciton and charge carrier, but also broaden the applications of this new kind of organic dots in the field of energy conversion.

Spontaneous synthesis of Ag nanoparticles on ultrathin Co(OH)2 nanosheets@nitrogen-doped carbon nanoflake arrays for high-efficient water oxidation

The slow four-electron transfer of the oxygen evolution reaction (OER) greatly limits the water splitting efficiency, so the development of high-efficiency and stable OER electrocatalysts is of great significance for large-scale alkaline water splitting. Herein, we reported an efficient self-supported OER electrocatalyst of Ag NPs decorated ultrathin Co(OH)2 nanosheets supported on nitrogen-doped carbon (NC) nanoflake arrays on carbon cloth (Ag/Co(OH)2@NC/CC). Our designed 3D unique electrode structure with heterointerfaces and hierarchical nanosheets endow Ag/Co(OH)2@NC/CC with outstanding OER electrocatalytic activity (300 and 350 mV at 50 and 100 mA/cm2, 79.8 mV/dec of Tafel slope) and good long-term durability in 1 M KOH. Furthermore, the related results of electrochemical tests show that the improved conductivity, increased electrochemical active sites and enhanced intrinsic active sites explain the superior OER performance. Our study will offer some new ideas in constructing new highly-active materials for various other energy conversion fields.

Construction of NiCo-LDH vertical standing arrays on carbon fibers for highly effective supercapacitors and catalytic oxygen evolution applications

Layered double hydroxides (LDH) have attracted a lot of attention in the field of energy storage and energy conversion due to their unique properties. However, it is still challenging to obtain LDH electrode materials with efficient energy storage and electrocatalytic properties simultaneously. In this work, NiCo-LDH with a vertical standing form was grown on defect-rich carbon fibers through an in-situ growth strategy to obtain a bifunctional self-supporting electrode with an "organ-pipe cactus"-like structure. This three-dimensional structure not only ensures high quality loading of NiCo-LDH nanomaterials, but also allows close contact between the active material and the conductive substrate, which greatly shortens the ion diffusion path. The prepared NiCo-LDH@CC self-supported electrode exhibits excellent cycling stability with a capacitance retention rate of 93% after 8000 cycles at 15 A g−1. In addition, the NiCo-LDH@CC composite has an ultra-low oxygen precipitation overpotential of 372 mV at 10 mA cm−2, which is superior to most reported non-precious metal-based bifunctional catalysts. These results suggest that the design of NiCo-LDH@CC self-supporting electrodes offers new ideas for the realization of efficient multifunctional nanomaterial applications.

Single-atom nanozymes: From bench to bedside.

Single-atom nanozymes (SANs) are the new emerging catalytic nanomaterials with enzyme-mimetic activities, which have many extraordinary merits, such as low-cost preparation, maximum atom utilization, ideal catalytic activity, and optimized selectivity. With these advantages, SANs have received extensive research attention in the fields of chemistry, energy conversion, and environmental purification. Recently, a growing number of studies have shown the great promise of SANs in biological applications. In this article, we present the most recent developments of SANs in anti-infective treatment, cancer diagnosis and therapy, biosensing, and antioxidative therapy. This text is expected to better guide the readers to understand the current state and future clinical possibilities of SANs in medical applications.

The Shockley–Queisser limit and the conversion efficiency of silicon-based solar cells

According to some estimates, every hour, Sun provides planet Earth with more energy than humankind consumes in a whole year. Part of this energy has been essential to ensure living conditions (warmth and food production, for instance) and, more recently, to generate electricity by means of atmospheric (aeolian) and/or geographical (hydropower) sources. In addition to these, the direct (photovoltaic PV) conversion of solar radiation into electricity represents a very elegant method of power generation that causes minimum (or no) environmental disturbance. As a result, numerous efforts have been dedicated to further advance the achievement of clean and sustainable electricity, as supplied by the PV science and technology. Within this scenario, the association of PV with the silicon (Si) semiconductor industry played a crucial role–either by introducing new scientific insights or by promoting successive costs reductions in the field of renewable energy conversion. Yet, the performance of these so-called (either crystalline or amorphous) Si-based solar cells was always a matter of concern. In fact, the subject gained attention with the seminal work by Walter Shockley and Hans Queisser that, in 1961, proposed a model according to which the maximum efficiency of a solar cell is determined by both the solar spectrum and the properties of the semiconductor material. Since then, the work by Shockley and Queisser (also known as the Shockley–Queisser limit) has experienced some improvements and became a reference in the field. Motivated by these facts, along with the main scientific–technological achievements they provided, the Shockley–Queisser limit and the conversion efficiency of the Si-based solar cells along the last 60 years form the basis of this paper.

Fe3Se4 rice grains anchored on cotton-derived porous carbon network for enhanced sodium ion storage and hydrogen evolution reactions

Transition-metal selenides have been regarded as promising anode materials for energy storage and conversion fields. However, their practical application is hindered by volume expansion, polyselenide dissolution, and sluggish kinetics. Herein, porous Fe3Se4 rice grains were successfully encapsulated on cotton derived carbon network (CN@Fe3Se4@C) by facile solvothermal method combined with in-situ selenization process. Beneficial from the unique structure, the CN@Fe3Se4@C electrode exhibits excellent sodium storage properties (302 mAh g−1 at 500 mA g−1 after 500 cycles) and hydrogen evolution reactions (HER) performance (an overpotential of 168 mV at a current density of 10 mA cm−2, and a low Tafel slope of 77 mV dec−1). Electrochemical mechanism investigations demonstrate that the carbon coated porous Fe3Se4 nanoparticles and ant nest-like carbon network can shorten the diffusion path for Na+ ions and suppress volume expansion. Meanwhile, the 3D interconnected porous carbon framework can provide multiple channels for fast electron transport and improve electron conductivity. In addition, the thin amorphous carbon layers on individual Fe3Se4 rice grains can well inhibit the shuttle effect of polysulfides and the agglomeration of Fe3Se4, ensuring fast kinetics and long-term stability. This study reveals the great potential of CN@Fe3Se4@C as active materials for sodium ion batteries and hydrogen production.

KOH-assisted aqueous synthesis of ZIF-67 with high-yield and its derived cobalt selenide/carbon composites for high-performance Li-ion batteries

To solve the environmental pollution and low yield during the sythesis of zeolitic imidazolate frameworks (ZIFs) and their derived materials, a KOH-assisted aqueous strategy is proposed to synthesize cobalt zeolitic imidazolate framework (ZIF-67) polyhedrons, which are used as precursors to prepare cobalt selenide/carbon composites with different crystal phases (Co0.85Se, CoSe2). When evaluated as anode material for lithium ion batteries, Co0.85Se/C composites deliver a reversible capacity of 758.7 mA·h·g−1 with a capacity retention rate of 90.5% at 1.0 A·g−1 after 500 cycles, and the superior rate capability is 620 mA·h·g−1 at 2.0 A·g−1. The addition of KOH accelerates the production of ZIF-67 crystals by boosting deprotonation of dimethylimidazole, resulting in rapid growth and structures transition from two-dimensional to three-dimensional of ZIF-67 in aqueous solution, which greatly promotes the application of MOFs in the field of energy storage and conversion.

Regulation of Outer Solvation Shell Toward Superior Low-Temperature Aqueous Zinc-Ion Batteries.

Aqueous Zn-ion batteries are well regarded among a next-generation energy-storage technology due to their low cost and high safety. However, the unstable stripping/plating process leading to severe dendrite growth under high current density and low temperature impede their practical application. Herein, it is demonstrated that the addition of 2-propanol can regulate the outer solvation shell structure of Zn2+ by replacing water molecules to establish a "eutectic solvation shell", which provides strong affinity with the Zn (101) crystalline plane and fast desolvation kinetics during the plating process, rendering homogeneous Zn deposition without dendrite formation. As a result, the Zn anode exhibits promising cycle stability over 500h under an elevated current density of 15mAcm-2 and high depth of discharge of 51.2%. Furthermore, remarkable electrochemical performance is achieved in a 150mAh Zn|V2 O5 pouch cell over 1000 cycles at low temperature of -20°C. This work not only offers a new strategy to achieve excellent performance of aqueous Zn-ion batteries under harsh conditions, but also reveals electrolyte structure designs that can be applied in related energy storage and conversion fields.

Analysis of the energy conversion properties and applications of Nanofluids: A review

Nanofluids have evoked extensive interest from researchers around the globe due to their distinctive thermo-physical properties and numerous potential benefits and applications in important fields such as energy, aerospace, electronics, vehicles and biomedicine. This paper summarizes the latest research about the heat transfer characteristics, fluid characteristics, and its influencing factors, influencing rules, and influencing mechanisms of nanofluids. It summarized the preparation, stability, thermal conductivity, specific heat capacity, light absorption characteristics and photothermal conversion performance of nanofluids based on the categories and influencing factors of nanofluids, and analyzed their laws and mechanisms. The purpose of this paper is to summarizes the latest research findings in the open literature on nanofluids, so that researchers in the field of energy conversion have a more detailed and clear understanding of the energy conversion properties and applications of nanofluids.

Recent Developments of Methanol Electrooxidation Using Nickel‐based Nanocatalysts

AbstractStudies of methanol electrooxidation reactions have achieved considerable advancements in the recent years for their encouraging contributions in the exciting fields of energy conversion and storage, organic syntheses, wastewater treatment, sensing, medicinal and environmental analyses, and many others thriving fields of modern technology. Accordingly, the fabrication of less expensive, efficient and decent quality electrocatalysts with high material stability, faster electro‐oxidation kinetics, as well as less carbonation and decent corrosion inhibition activities are highly urged. Consequently, scientists around the globe are in continuous search for alternative economical smart anode‐nanocatalysts for methanol oxidations with superior electrochemical performances. In the recent years, various inexpensive and readily‐available nanocatalysts of non‐noble metals like Ni, Co, Cu, etc., in reference to electrooxidation of organic molecules have been reported. The present work highlights the recent progress accomplished by rapidly flourishing nickel‐based electrocatalysts for electrooxidation of methanol. The discussion comprehensively includes the basic mechanistic understandings and fundamentals for achieving high efficacy of methanol electrooxidation with nickel‐based electrocatalysts. Also, the current challenges faced in this emerging area have been outlined to achieve superior, productive, and commercially viable catalysts for methanol electrooxidation in the near future.

Simple preparation of amorphous nickel boride/Mn0.5Cd0.5S composite and its high-efficient photocatalytic performance for hydrogen production

In this paper, amorphous NiB-modified Mn0.5Cd0.5S (NBMCS) was facilely prepared by a simple stirred method. The results showed that NBMCS possesses better light absorption ability, better separation capability of photogenerated carriers, lower overpotential and stronger reduction capacity. When NBMCS was applied for splitting water to H2, it was found that the hydrogen precipitation rate was 195 times higher than bare Mn0.5Cd0.5S and 4.6 times higher than 1 % Pt/ Mn0.5Cd0.5S, and it showed good stability. Therefore, an inexpensive and effective cocatalyst replaced Pt was shown, which might be diffusely used in the solar energy conversion field.

Carbon-based hole storage engineering toward ultralow onset potential and high photocurrent density of integrated SiC photoanodes

In the present work, we report the exploration of integrated photoanode based on SiC nanohole arrays with a rationally designed amorphous carbon nanolayer. The SiC nanoarrays are fabricated via anodic oxidation, and the carbon outlayers are introduced by chemical vapor deposition (CVD) process, respectively. In such case, the active materials of carbon outlayer coated SiC nanoarrays (SiC@C) and current collector of the unetched SiC wafer are established into a whole structure without interfaces, thus favoring the formation of integrated photoanode. It is verified that the coated carbon nanolayer acts as an efficient hole storage layer, which effectively drives the separation of photogenerated carriers. Consequently, the as-fabricated SiC@C photoanode exhibits excellent photoelectrochemical (PEC) water splitting properties with a high solar-to-hydrogen efficiency of 2.67%. Moreover, it delivers an ultralow onset potential of −0.049 V (vs. RHE) and a high photocurrent density of 5.0 mA/cm2 (1.23 V vs. RHE), superior to those of intrinsic SiC counterparts and most SiC nanostructures ever reported, implying their promising applications in the field of solar energy conversion.

Rational design of boron nitride with different dimensionalities for sustainable applications

The application of boron nitride (BN) nanomaterials in various fields received extensive attention in the past decades, attributed to its extraordinary characteristics: high surface area, low density, excellent thermal stability, mechanical strength, bio-compatible, and excellent corrosion resistance and antioxidant. This article starts reviews the research progress in the synthesis of BN nanomaterials with different dimensions, followed by briefly summarizing the commonly used preparation methods and main applications of BN nanomaterials, focusing on their potential applications in the fields of environmental remediation, energy conversion (oxygen reduction, nitrogen reduction, hydrogen evolution, fuel cell), and biomedicine. Finally, the research prospects of BN-based nanomaterials are proposed, including the challenges for the large-scale preparation of BN nanomaterials and mechanism research. It is expected that this review is beneficial further to understand the current status and properties of BN-based nanomaterials, to promote research and development of the BN nanomaterials in various fields.

Recent developments of polysaccharide‐based double‐network hydrogels

AbstractPolysaccharides possessing distinctive properties, such as biocompatibility, biodegradability, and nontoxicity, are promising matrices for hydrogels. However, the polysaccharides‐based hydrogels have poor mechanical properties, which is a major limitation for their applications. In recent years, researches on double‐network (DN) hydrogels with outstanding mechanical properties have gained increasing attention. Therefore, the main research orientation is to combine the benefits of both materials and broaden their applications in various fields. This paper reviews the recent progress of polysaccharide‐based DN (PDN) hydrogels that show great advantages in mechanical, physiochemical properties, biocompatibility, biodegradability and so on. The preparation, structure, and unique properties of different PDN hydrogels are discussed in detail. Moreover, we summarize the applications of PDN hydrogels in biomedical and energy storage and conversion fields. This research progress is breaking through the limitations of PDN hydrogels and opening a new avenue for their future development.